Fire-door-releasing mechanism.



E. A. LOWE.

FIRE DOOR RELEASING MECHANISM.

APPLICATION FILED JUNE 17.1913.

1 ,269,556. Patented June 11, 1918.

3 SHEETS-SHEET l- WIT "E8858 j "IVE/(TOR 7 W ERA/SSTALOWE. W 9146M E. A. LOWE.

FIRE DOOR RELEASING MECHANISM. APPLICATION FILED JUNE 17. I9l3.

1 269,556. Patented June 11, 1918.

3 SHEETS-SHEET 2.

I/VVEIVTOR [RA/EJTALOM/f wile/W E. A. LOWE.

FIRE DOOR RELEASING MECHANISM.

APPLICATION FILED JUNE 17. 1913.

1,269,556. Patented June 11, 1918.

3 SHEETS-SHEET 3 Hm. a 3

l- @8858 3d) 6 ,6 31 30 mvuro ZWW 41 k f/F/VFSTA 4014 5 vwm if 43 2 45 BY ATTORNEYS.

' STATES, PATENT o EIcE.

vin'm-E's'r A. LOWE, o Nomn PLAIEEIEED, N W JERSEY, AssIeNon T LowE MANU- rncrunme oomrm,'o1*rLAmEIELn, NEW JERSEY, A conroaarron 0E NMEW JERSEY.

-' FIRE-.DO'QR-RELELSING mEcnAmsm.

Specification ofLetters Patent. P tel lted J line 11,

Application filed June 17, 1913. Serial No; 774,101.

To all whom it mayconcem;

Be it 'knownJthat I, EBNES'1 A. LbwE,

a citizen of the United States, and a'resij dent of North Plainfield, in the county of Somerset and State of New Jersey,'have invented certain new and useful Improvements in Fire-Door-Releasing Mechanism,

of which the following is a specification.

My invention relates to releasing mechanism automatically controlled through changes of temperature and serving to bring about'the automatic closing or opening of a gate or'barrierin a passage or opening of kind. 16 any:

or the sake of illustration, however, my invention will be described with reference to a door located in a partitionand designed 0 automatically close on the occurrence of My invention however is not confined to use with doors in the limited sense of the :term but may be applied to windows, shutters, or other devices, and to such devices when normally closed and caused to open automatically on the occurrence of fire, as is sometimes required in order to allow the escape of smoke, as for instance in the well of a fire escape, or to divert a draft of air.

Ordinarily such doors are held open normally by the use of a counterbalance weight attached to the door, thus allowing the door to move freely or to be held readily in any position, .whereby said door may be employed in the usual way of doors and opened or closed at will by'anyo'ne desiring to pass through the opening.

To avoid danger from fire arising from the door being left accidentally open, the ordinary practice heretofore has been to add a protective device consisting of a fusible link connected to a cord, by which the-counterbalance is sustained, so that in case of fire .the melting of the link will release the rope and allow the counterbalance to fall or become disconnected from the door, thus allowing the door to respond to the action of gravity and to close.

This fusible link of a great deal of crlticism as, being a fixed protection. is the source bility of the fire communicating through the open doorwTy before the link operates and the door 0 os'es; 1n fact this is what happens in the majority of times, and to insure the positive releasing of the weight.

of expansion per degree of temperature rise,

this device, instead of depending for its operation upon the. temperature to reach a certain maximum, such as' the fusible link or fixed temperature device does, is made to operate when the temperature rate per minwithout regard to initial or maximum tem 'ute advance reaches a certain minimum perature'. V In other words, a rate of rise instead of a fixed temperature principle is employed for its operation.' As the pres-' ence of fire causes the temperature to ad- Vance very rapidly per minute and ;far above the advance from any local cause, such as light, heating, atmospheric, or manufacturing, it is obvious that the rate of rise temperature device needs only to have a compensating, device making it respond only to that rate of temperature rise over and above the temperature advances from abnormal local conditions to have the device operate only from fires and not from tem- -perature advances caused by other conditions,and this is exactly what this new in-v vention does in practice.

This compensating device consists of a;

relief vent 'leadin" from the air-chamber,"

and having a pre etermined leak adjusted to" relieve the pressure in the air-chamber up to any predetermined pressures caused by certain rates of temperature rises, but not to relieve that pressure arising from rates of temperature. advance caused by fires,

which are very excessive and violent. The

difference between rates of temperature advances'from fires and local or ordinary heating are shown by" the expernnents and .tests made by the National Board of Fire'Underwriters, showing thata four-degree rate of temperature rise safely covers the temperature advances from all local conditionswexcept actual fires, when the temperature-advance is very marked and violent. I find from actual and continued experiment in practice that fires cause the temperature to advance near the fire from 4 to 100 degrees per minute, according to local conditions and the size and class of the fire. As small a fire as a few sheets of paper, pile of rub-- bish,.0r an alcohol fire say 3 feet square will raise the temperature nearby from 25 to 50 degrees per minute. In actual practice with this door release device I find 3 sheets of common newspaper or an alcohol fire 17 feet square placed 25 feet from the door opening will operate the device in from 25 seconds .to seconds. At the same time the device which ways, as herein described, is to mechanically release a counterbalance weight used to-counterbalance a fire door. The airchamber or air-chambers are preferably so constructed that the inclosed volume of air is readily affected by any change of temperature, a favorable form being that of thin metal balls, one or more, connected to a pressure responsive means one wall of which is flexible and yields to the expansion of the air inside. This flexible wall of the air-chamber or diaphragm in its line of travel moves a pin or plunger,which in turn operates or controls the necessary gears or levers so arranged that a weight will be released by the expansion of the confined air.

While I prefer to employ an air thermostat such as described, provided with an automatic compensation for normal changes or rates of change of temperature, such as above indicated, it is not to be understood that my invention-is limited to such special thermostat, since many of the devices and combinations of devices hereinafter described and shown in the accompanying drawings may be used with other forms of thermostat acting by change of temperature to release the mechanism which permits or causes the door to close.

One of the many forms of construction by which my invention may be carried out is shown in the accompanying drawings.

My invention consists in the construction and combinations of apparatus hereinafter described and more particularly specified in the claims.

Figure 1 shows a self-closing fire door equipped with apparatus constructed cordance with my invention.

Fig. 2 is an enlarged elevation of a portion of the apparatus.

Fig. 3 is a vertical section on the line 33 Fig. 4.

Fig. 4 is a plan of the apparatus, the easing being shown in horizontal section.

Fig. 5 is a section through the apparatus on the line 55 Fig. 4.

Fig. 6 shows a portion of the releasing mechanism detached and in normal position.

Fig. 7 shows the same parts of the mechanism with the parts in released position.

Fig. 8 is a plan and partial section of the in acapparatus through the chamber containing.

the diaphragm which responds to the in creased pressure of the air when heated in the air-chamber.

Fig. 9 is a detail showing in section the air vent for the air-chamber, whereby a compensation is obtained for normal rates of rise of temperature so that the thermostat will not operate to release the door.

Fig. 10 is a detail showing in section the connection of the air bulbs of the thermostat to the common union or chamber, which in turn communicates with the space containingrthe diaphragm of the thermostat.

ig. 11 shows a detail of the operating spring and train of wheels of the clockwork mechanism.

Fig. 12 is a detail view showing a pawl and an arm 'joined thereto, whereby the devices are freed from the detaining mechanism' controlled by the thermostat in case of the breakage of the main spring and are thereby left free to the action of'a supplemental spring as hereinafter more partlcularly described.

1 indicates a door adapted to close an opening in the wall 2 and sustained upon inclined ways 3 in the usual manner, so that when left free to the action of gravity it will move and close said opening.

t is a counterweight sustained by thecord 5, which connects at one end with the door, as shown, and passes over a pulley 6 fixed to the wall or other suitable support and.

around a wheel or pulley 7 carried by the weight. 100 indicatesthe fusible link connected to said cord and to which reference is heretofore made. The free or opposite end of said cord at 8 is knotted and is sustained in the slot of a pivoted arm 9 forming a slip hold, which, bein normally sustained or held by a detent in t 1e position shown in Fig. 2, will prevent the weight from drop ping to the floor. Then, however, the detent is released and the arm permitted to turn downward by the influence of the weight, the cord will slip from its hold in the yoke or hook formed by the arm 9 and the weight 4 will drop to the floor and the door 1 will close, .being free from the re detent mechanism normally holding said re- 'straint of the, counterweight, in obvious The arm 9 is, in effect, a release device immediately associated with the door and which acts to free the same by freeing itfrom the influence of the restraining device comprising, in this instance, the weight or counterweight which opposes the continual bias'of-the weight tending to close the door. Combined with said release device I employ lease device out of action and comprising preferably a train of "detents some of which, near the release device, are perferably constructed to have a self-releasing tendency.

The final member of said train or that which is immediately'controlled by the rate of rise thermostat is preferably held in normal position by a positive lock or'dog which is moved out of .the' way'to free the detent mechanismas a whole by the force of expansion-ofthe air of the rate of rise thermostat when pressure accumulates therein owing to its exposure to a temperature whose rate of rise exceeds the normal or safety rate. Such detent mechanism may be constructed as follows:

10 is a rock shaft to which the arm or lever-9 is secured and with which said arm turns, as on a pivot. A suitable weight 11 7 may be connected to said arm and rock shaft to cause these parts and the other parts carried by them to be automatically restored to normal position by gravity after release of the -door 1. Secured also to the rock shaft 1 1O isan arm 12 forming the arm of the detent, and which is normally locked in position shown in Fig. 6, by a suitable catch that erably of the form shown andnowto be paris caused to free the arm 12 and consequently the weight 4 by the .operationof the thermostat and the intermediate. mechanisms of any suitable character or form but prefticularly described. When. thedetent arm 12 is so freed, it swings up into the position shown in Fig. 7

- under the action of the'wei'ght 4 and the knotted end of the cord slips oifthe hook of the arm 9 and frees theweight inobvious manner. r v I v In the preferred manner of carrying out my invention I employ a second or interme diate trip or detent arm 13 formed as shown more clearly in Figs. 6 and 7 with a shoulder at 14 adapted to form a catch or trip for the end of the detent arm 12. When the detent arm 13 is held against the influence of its spring 15 in position shown in Fig. 6 and the end of the detent arm' 12 is engaged beneath the shoulder 14 as shown in that figure, the weight 4 will be sustained;

but when the arm 13 is released and allowed to move under. the influence of the spring 15, it will turn to position shown in Fig.7 and release the detent arm' 12, which will thereupon -fly up to position shown in' Fig. 7 and cause the door 1 to close, ifnot already in closed position.

The-detent arm 13 is mounted upon and turns freely on a second rock shaft 16 and is provided with a pin 17. adapted to be eng'aged by the arm 18 carried by said shaft. aid shaft 16 is provided with an operating handle 19 which is the re-setting handle for re-setting the 'mechanism after operation and for likewise rewinding the spring of the spring-driven clockwork or motor shown after each operation thereof. ,Besides engaging the pin 17 to re-set the detent arm 13, the said arm 18 operates upon other devices to be presently described. I V

The release of the arm 12 by the freeing of the arm 13 to allow the said arm 12 to turn to position shown in Fig. 7, under the influence of the weight 4, and so as to free the same, will be followed upon the release of said weight by the automatic restoration which, is formed as shown at .22 or in any other suitable mannerto act as the'detent for normally locking the detent arm 13 when the parts are set. When the, shaft is released and permitted to turn in the direc r 'tion of the arrow Fig. 6, the part 22 as sumes the position shown in Fig. 7, thereby releasing the detent arm 13. The resetting of the arm 13 by the re-setting arm 18 acting through the pin '17, which carries the arm 13 to position indicated by the dottedlines in Fig. 7 followed-by the re-setting of the shaft 20 to turnthe lock 22 back into 'position shown in Fig. 6, will cause the arm 13 to be. locked or detained and the arm or detent 12 .to be held in readiness for another operation.

The re-setting of the shaft 20 against the influence of the means tending to turn it so as to free-the detent arm 13 is effected by the use of the re-setting handle 19 acting on said shaft 20 through the rock shaft 16,

arm 18 and the slotted link 23that engages by its islott'ed part a pin 24 projecting from the arm 25 carried byshaft 20-01 the extension 21 thereof, as shown in Figs. 7 and 8.-

Theshaft is given a bias in a direction to turn so as to free the arm 13 by means of a spring 26 havingone end fixed to post 27 and the other attached to the shaft 20 and said spring is re-set or' re-wound' by the re-setting of the shaft as just described.

The remaining portion of the detent mechanism up to the final member, which is' actuated bythe rate of rise thermostat, may be constructed as follows:

29 is a gear wheel and 30 a ratchet wheel secured together and adapted to turn freely on the main shaft 20, while 31 is a pawl carried by-said main shaft by means of an arm 32 or in any other suitable way, which pawl -is adapted to ride over teeth of the ratchet wheel 29 freely when the shaft is turned to rewind the spring,'but will engage with a tooth of said ratchet when the spring attempts to unwind and in the unwinding operation. Wheel 30 gears through an intermediate wheel 33 in the manner usually employed in a clock train of wheels or in any other suitable manner with an escapement wheel 34. The retarding escapement 35 or rock shaft carrying the same is provided with an arm or fly 36 bent around or extended for enga ement. by a detent 37. When engaged y said detent 37 the train and consequently the shaft 20 are'locked from movement 'but I when the fly or arm 36 is freed from the detent 37 and the escapement may'oscillate freely, the shaft turns with a retarded motion and by the means 22, as already described, controlling the operation of the releasing mechanism for the door, causes said door to close. The detent 37 is upon the end of an arm 38 pivoted at 39 upon a bracket 40 carried by the clockwork frame and is provided with a s ring 41, which throws the detent 37 and rees the escapement and shaft 20 when the end of the arm or lever 38 is released from the catch or detent 42, as shown clearly in Fig. 8. The catch or detent 42 might be likewise pivoted, as shown at 43, on a stud of the frame of the apparatus and is itself provided with a spring 44 normally tending tohold it in the position shown in the same figure. One end of the catch or detent lever 42 is engaged ner but preferably by the action of a hook 46 (see 'Figs. 3, 4, 5 and 8) mounted upon the arm 18 of the rej-setting rock shaft and adapted to engage and re-set the catch or detent 37 and to move the longarm of the lever 38 back over the end of the detent arm 42 and into position where the spring 44 ma pull'said arm up into position to latch or catch the lever 38 until the recurrence of incense the operation of said arm 42 by the ther- 47 indicates sealed metal bulbs of any desired number containing air and com-- municating through bulb-stems 48 with a common sealed union or air-chamber '49.

The rearward extension of the latter is fastened to a frame or support 50, which in turn is secured to the casing 51 or other suitable support. A pipe 52 leads from the chamber 49 or the extension thereof. and

is joined by the coupling; 53' to a pipe 54' leading, as shown more particularly in Fig. 8, from a sealed, flat. chamberor casing 55, containing a flexible'diaphragm 56 clamped between the halves of the casing with an air-tight joint. The plunger 45 is carried by the flexible diaphragm 56, so

that when the air in the chambers or bulbs '47 expands and -'-the increased pressure transmitted through the pipes and connections to the lower face of the diaphragm 56causes the same to bulge, said pin or plunger 45 will act on the latch or detent lever already described and release the detent lever 38 thus freeing the actuating spring 26 and causing the shaft 20 to rotate under the action ofsaid spring. a Communicatin with the air-chamber 49 is'an air vent o the character already described. This air vent may be mounted in an extension 57 from the air-chamberfthe end of which extension being provided with v a detachable screw, cap 58 sealing the end of said pipe or extension 57 and carrying a vent pipe 59, the inner end of which pro jects into the air space within the pipe 57. The air vent pipe 59 is preferably packed with air-filtering material, as indicated at 6.0, and its inner end has its bore or passage restricted in diameter to any desired extent required to determine the rate of escape of air from the chamber whenthe pressure rises therein, due to the increase of external temperature.

This vent pipe 59 is preferably made of soft metal so that its inner end may be readily compressedv or crimped to restrict the air vent or limit the rate of escape of air when the pressure rises. Theextent of the leak predetermines the rate of escape and therefore the rate of rise of temperature afl'ecting the bulbs that is necessary to cause the internal pressure to rise and operate the thermostat plunger 45. With an air. vent having a comparatively free passage to allow ready escape of ,air, the rate of temperature rise necessary in order that the diaphragm 56 may be caused to bulge will have to be at a greater rate than Would be sons to more greatly limit or interfere with the rate-of escape.- In the latter case it is obvious that a lesser rate of 'rise of term ternal pressure will causethe diaphragm 56 to operate. With a normal rate of rise of temperature the air willescape by-the vent at a suflicient rate to prevent the internal pressure rising so as to operate the device I have shown the air thermostat mounted.

upon the same frame 'or support as the mechanism which controls the release of the door but it is obviousthat. the bulbs 47 and the associated parts forming the air expansion chamber could be mounted in any desired location and coupled by apipe 54; of the required length with the air-chamof the device. The bulbs47 of any desired number constitute an air heating chamber.

having heat-conducting walls of large superficial extent, the object being to render the .contained air sensitive to changes of external temperature.

any particular construction or form of airchamber for the thermostat and said airchamber, instead of being composed of one or more bulbs and attached parts, might be of any other desired form. v

In order to signal the location of the door which is operated a characteristic signal paratus so as to operate upon the release or movement of the master or controlling shaft 20 is provided. Said signal transmitter is also used as a tell-tale to give warning .or notice of accidental breakage of the operating sp 26, which would obviously render the evice inoperativeand would require that immediate attention be given to restoring the apparatus to working condition. Said signal transmittermaybe associated with and brought into action by the operation of the apparatus in any de-' slred manner, but it is preferable to control it-dii-ectly bythe movement of said shaft 20, for which purpose said transmitter may be provided with a trip or release engaged by the arm 25 projecting-from shaft 20.

The signal transmitter itself is typified by the spring-actuated signal wheel 61 and contact spring 62 adapted to be engaged by the teeth or projections of wheel 61 andto thereby'send the characteristic signal assigned to the particular door or controlling mechanism therefor, indicating its location; The signal may translated or received on bell 63 or other suitable tell-tale orsignal receiving apparatus, as indicated. The re-' lease-of signal wheel 61, which normally tends to rotate. \mder the influence of its 1' spring, is effected by the release arm 64,

her containing the operating diaphragm 56 transmitter. suitably connected with the ap- 6. against turnin which normally detains the detent arm 65 I connected-to the shaft carrying the signal Wheel. The release lever or arm 64 is arranged in the path of the arm .25 and so 5 perature'and consequent rate of rise of' in-;-'

that the saidarm, on the unwinding or re- "As a measure of safety and in order. to insure the operation of the apparatus in case of accidental breakage of the spring the other to the end of the arm 25 secured .15 5 26, pending the repairofthe apparatus, the

to the shaft 20. Said spring 66 1s under tension and tends to pull the arm 25 overand with it turn the shaft 20 in the same way that the spring 26 turns it when freed from the detaining action of the catch or detent 37.

In order that the shaft may be free to rotate under the influence ofthe spring '66 in case of breakage of the spring 26, means My invention, however, is not limited to' coupling the said shaft 20 from the clock-- work train connecting said shaft with the escapement and fly. For this purpose the pawl 31 which engages the ratchet wheel 29 is provided with'a tail-piece or extension 67, which projects over into the space surroundingthe spring 26, and so that, when the said sprlng breaks and expands, its outer layer] will engage the tail-piece- 67 and lift the pawl out of engagement with the ratchet wheel. This obviously uncouples the shaft from the detaining action of the catch 37 and thermostat, and sothat the Spring 66 will turn said shaft and produce not only a closing 6f the door, but by operating the signal transmitter and bell or other tell-tale .will give notice of the fact that an abnormal action of the apparatus has occurred,

- due to the breakage of the spring 26,

.The general operation of the apparatus ,is' as follows:

' Normally the weight 4. is sustained by the cord 5 which engages the hook 9, the latter being held: up by the engagement of the detent arm 12 with the latch or catch 14 uponthe detent. arm 13, which'latter is at such timelocked bythe lock 22 carried by shaft 20 held in position'ilitlicated' in Fig.

moving under the influence of spring 26 by the catch 37 en aging the fly 36 of the clock train, as alrea' y explained, and-the catch by the'action of the. -spring 26. The s aft 20iS-detained from I 37 is; itself detained by the men or cateh' 42, the diaphra 56 beingat such time- -.re1axed or sub ect to substantially equal 7O verse movement of the shaft 20, w1ll releasev the signal device.

atmospheric pressure upon its opposite surfaces respectively.

During normal atmospheric changes of air within the air-chamber escapes by the vent at such rate that the pressure-will remain substantially equalized and the actuating pin 45 remain depressed. 'On rapid change of external temperature, due to fire, the pressure in the air-chamber rises rapidly and the internal air pressure is not relieved at a sufiicient rate by the air vent to prevent an excess of pressure upon the lower side of the diaphragm 56, which thereupon rises and unlatches the detent arm 38, thus freeing the fly 36, so that the train may rotate by the action of the spring 26 communicated thereto through the pawl 31 and ratchet wheel 29. The shaft 20 now turns under the action of the spring 26 andthe part 22 rotates to position indicated in Fig.

, 7 thus freeing the arm 13, which assumes the position shown in full lines in. said Fig.

7 and frees the arm 12. The hook 9 is thereupon freed and the knotted end of the cord slips off its hold on the hook 9, thus freeing the counterweight 4 and'leaving the doorfree to act by gravity and close.

The operation of the parts thus described produces also an operation of the vsignal transmitter and sends the. desired characteristic signal, as already set forth.

When the weight frees itself from the hook 9, the latter, with its rock shaft, immediately resumes the'normal position under the influencev of the weight 11, so that the arm 12 is restored to position indicated in dotted lines in Fig. 7, its movement to such position not being obstructed by the lever 13, because the latter is at such time in the position shown in the full lines in Fig. 7.

To re-set the parts and rewind the spring 1 26, as well as to put the spring 66 "under additional tension, the re-setting lever 19 is operated, thus operating the arm 18 and the slotted link 23 connected therewith. The first portion of the movement of the slotted arm 23 is a lostv motion or without action upon the pin 24 and arm 25, so that the part 22 will temporarily retain theposition shown in Fig. 7. During this lost motion, however, of the slotted link 23, the'arm 18,

by the pm 17, turns the arm 13 from the po-' sition shown in fulllines, Fig. 7, to, or slightly beyond, the position shown in dotted lines in said figure. When this re-setting movement of the arm 13, which obviously brings it around into position to again lock the arni 12, has been accomplished, the link 23 becomes coupled to the pin 24 at the end of its slot and thereby turns the arm 24 and with it the shaft 20 and part 22 into the position which is shown in Fig. 6, thereby locking the arm 13 in position set. This movement of the arm 25 by the action of the arm 18 rewinds the spring 26 and carries the pawl 31 around to position to engage a fresh tooth or teeth of the ratchet 29, in which position the shaft is held because the spring 26 cannot unwind owing to the detaining action of the parts coupled up thereto through the pawl and ratchet, said detaining parts having been reset at the same. time with the re-setting action of the arm '18 upon arms 13 and 25 by the operation of the projection or car 46 already referred to and carried by arm 18, which, in such re-setting movement, engages the short end of the detent lever 38 so as to carry the detent 37 into position to be engaged by the fly arm 36 and at the same time moves the opposite or long end of the lever 38 back past the end. of the catch or catch lever 42, so that it will become latched or engaged by the latter in position shown in Fig. 8. I

The re-setting of the signal transmitter or tell-tale is readily accomplished by simply restoring the arm 65 projecting from the signal wheel 61' to position to be latched by the detent arm 64. The parts shown, as will be well understood, merely typify the operating parts of the signal transmitter and do not include the wellknown retarding mechanism employed to retard the unwinding action of the operating spring.

of a confined body of air to mechanically free th detent mechanism.

2.- In an apparatus of the character described, the combination with a door, of a detent controlled releasing apparatus and a thermostat acting directly and mechanically by the force of expansion of heat upon a detent of said releasing apparatus and adjusted to operate upon any abnormal rate of change of temperature afiecting said thermo: stat.

. 3. In an apparatus of the character described, the combination with a fire door, or the like, of a release device, a; detent nor-. mally holding said release device out of action and a rate ,of rise thermostat having a compensating device adjusted to permit the thermostat to act upon a detent by power of expansion by heat only when the temperature rises at a greater than the normal rate. 4. In an apparatus of the character described, the combination with a fire door normally held out of action, of a fluid thermost-at provided with a compensating vent and means controlled by said thermostat for releasing said door.

5. In an apparatus of the character described, the combination with a counterweighted door, of sustaining means for said counterweight, a fuse acting in conjunction therewith to sustain the counterweight, a

releasing device for releasing the sustaining means, detent controlled mechanism for said releasing device and a rate of rise thermostat for actuating a detent thereof upon change of tem erature at an abnormal rate and indepen ently of the absolute temperature required to operate the fuse.

6. In an apparatus of the character described, the combination with a counterweighted door, of detent controlled mechanism for releasing the counterweight, an air thermostat having an air vent and acting by the direct mechanical effect of the expanding body of air therein to mechanically release the detent mechanism and a fuse sustaining said weight and adapted to free the same on. the attainment of an absolute temperature independent of the rate of rise of temperature which brings the air thermo- I stat into action.

7. In an apparatus for automatically releasing doors and the like, the combination with a door and the releasing devices therefor, of two controlling thermostats one an air thermostat having a compensating vent adjusted to cause the same to respond only when the temperature rises at an abnormal rate and independently of the attainment of a fixed temperature, and the other a fixed temperature thermostat con sisting of fusible material and adapted to act upon the attainment of a fixed temperature independently of its rate of rise.

Signed at Plainfield in the county of Union and State of New Jersey this 14th day of June A. D. 1913.

. ERNEST A. LOWE.

Witnesses:

W. R. TOWNSEND, F. M. DUNHAM. 

